uboot-layerscape: do not build efimkcapsule tool

OpenWrt layerscape target does not use this command. If the host is
missing gnutls, this tool will fail to build. Fix build error:

tools/mkeficapsule.c:20:10: fatal error: gnutls/gnutls.h: No such file or directory
   20 | #include <gnutls/gnutls.h>
      |          ^~~~~~~~~~~~~~~~~

Fixes: c773c3f ("uboot-layerscape: bump to lf-6.12.20-2.0.0")
Signed-off-by: Shiji Yang <[email protected]>
Link: openwrt/openwrt#19836
Signed-off-by: Robert Marko <[email protected]>

Author: DragonBluep

package/boot/uboot-layerscape/Makefile

@@ -151,6 +151,9 @@ UBOOT_TARGETS := \
   fsl_ls1021a-twr-sdboot \
   fsl_ls1021a-iot-sdboot
 
+UBOOT_CUSTOMIZE_CONFIG := \
+	--disable TOOLS_MKEFICAPSULE
+
 define Build/InstallDev
 	$(INSTALL_DIR) $(STAGING_DIR_IMAGE)
 	$(INSTALL_DATA) $(PKG_BUILD_DIR)/$(UBOOT_IMAGE) \